Centipede (Arcade)

That darn arthropod!

Unused Graphics#

In the test mode of the game, viewing the graphics, an unused Grasshopper enemy can be found. According to the developers, it was to serve the same role as the Spider does in the final game.

Anti-Piracy#

Due to a rise of copies and pirated arcade cabinets of previous games, Atari made increased efforts to prevent such cases in their arcade games starting from the 1980s. Like many of Atari's arcade games at the time, it will cripple gameplay if certain checksum checks fail. These checks were reimplemented for the game's sequel.

Copyright String Checksum#

During the title screen, the game runs a checksum of the "©1980 ATARI" copyright string and stores the result in 0xFF. If this value is not 1 due to changing the first A in "ATARI", then every 128 frames (about 0.5 seconds), the game runs arbitrary code from a register that easily breaks the game to the point of being unplayable.

Draw Copyright String Checksum#

The code to draw the copyright string is located at 0x2130. Whenever the copyright string is drawn on the title screen, the game runs a checksum on this code to see if the code to drawing the copyright string has been modified, and stores the result at 0xFE. If this value is not 0, the game crashes when starting a game due to loading an invalid address set by the value.

Genuine Hardware Check#

The game checks for a POKEY pseudorandom number generator chip to ensure that it is being run on genuine hardware from Atari. If the game is unable to generate a random number from the chip when the instruction to do so is called, the game freezes.

Hidden Message#

Sitting at 0x0000018D in the 136001-407.d1 ROM is eight or so seemingly innocent nonsense bytes with a clever secret - if you convert them to binary, then replace the 0s with a dot and the 1s with a dash, you get the sentence "COPYRIGHT 1980 ATARI" in International Morse Code! An updated version of this message is also present in the game's sequel.

According to programmer Ed Logg, this was used as a "code trap" with which to catch bootleggers in the act of ripping off Atari's code, and it was cited as such in at least one court affidavit.

        hex 02      bb      5a      30      5f      ee      7d      a8
     binary 0000001010111011010110100011000001011111111011100111110110101000
dots+dashes ......-.-.---.--.-.--.-...--.....-.--------.---..-----.--.-.-...
with spaces ...... -.-. --- .--. -.-- .-. .. --. .... - .---- ----. ---.. ----- .- - .- .-. .
    decoded        C    O   P    Y    R   I  G   H    T 1     9     8     0     A  T A  R   I